There is a growing demand for glass reinforced thermoplastics parts, particularly in the automotive industry. Glass fibers are used to reinforce the basic thermoplastic structure to improve the strength and impact resistance of the finished part. There are various methods of combining the glass fibers with the plastic. Molders of reinforced thermoplastics using direct long-fiber compounding are seeking a technology that allows the molder to produce a glass-mat thermoplastic (GMT) composite sheet. This development is driven by a desire to reduce raw-material costs by not having to buy a preconfigured sheet. Do-it-yourself compounding also gives GMT molders a means of reusing their scrap. Further savings can be gained by an immediate transfer of a freshly-made GMT sheet into a press while still pliable, which eliminates a need to reheat the sheet in a reheat oven.
Most current methods provide a glass/plastic matrix that is consistent throughout the geometry of the part. But there is considerable expense in creating a glass/plastic matrix and usually the same reinforced properties are not needed over the whole geometry of the part as only specific areas of the part need the greater reinforcement provided by the glass sheet.
U.S. patent application Ser. No. 2005/0156352A1 (Inventor: Burkle et al; Assignee: Krauss-Maffei Kunststoffiechnik GmbH) discloses a multi-stage injection molding process for production of multi-component reinforced plastic products involves forming a fiber preform in one area of an injection machine before moving to a molding area. Disadvantageously, since an endless band (which is a fibrous insert) is fed continuously into a molding machine, material is cut from the endless band to keep the endless band moving continuously through the molding machine, which permits subsequent portions of the band to be used in molding many articles. This arrangement leads to wasting fibrous material, and is potentially more costly to operate.
U.S. patent application Ser. No. 2004/0021247A1 (Inventor: Habisreitinger et al) discloses a press molding method for producing plastic shells from fiber-reinforced duroplastics. The method includes feeding sections of fiber mat into a molding press, spraying on resin onto the mat, closing the mold, allowing the resin to cure and trimming flash from molding. Disadvantageously, this reference teaches cutting excess material from an insert or molding. This arrangement leads to wasting fibrous material, and is potentially more costly to operate.
U.S. Pat. No. 6,495,091 (Inventor: Manson et al) discloses the manufacture of polymer or composite products while eliminating intermediate processing stages by combining at least two potential conversion steps for polymeric based composite manufacture, from reinforcing materials and matrices to finished products. Disadvantageously, this reference teaches cutting excess material from an insert. This arrangement leads to wasting fibrous material, and is potentially more costly to operate.